Synthesis of high quality carbon single-walled nanotubes

Abstract

Methods and processes for synthesizing high quality carbon single-walled nanotubes (SWNTs) are provided. A carbon precursor gas at reduced concentration (pressure) is contacted with a catalyst deposited on a support and at temperature about 10° C. above the SWNT synthesis onset temperature, but below the thermal decomposition temperature of the carbon precursor gas for given growth conditions. The concentration (pressure) of the carbon precursor gas can be controlled by reducing the total pressure of the gas, or by diluting with an inert carrier gas, or both. The methods produce SWNTs with the ratio of G-band to D-band in Raman spectra (I G :I D ) of about 5 to about 200.

We claim: 
     
       1. A method for synthesizing carbon single-walled nanotubes (SWNTs), the method comprising the steps of:
 providing a metal catalyst on a support wherein the metal catalyst and the support are in a mass ratio of between about 1:1 to about 1:500; 
 contacting the catalyst with a carbon-containing gas selected from a group consisting of methane, ethane, propane, butane, pentane and hexane at a partial pressure of about 5 torr to about 200 torr, and the total pressure of the gas is about 740 torr to about 780 torr; and 
 providing a reaction temperature between about 600° C. and 1200° C., wherein SWNTs are synthesized with a ratio of G-band to D-band in Raman spectra (I G :I D ) of greater than about 100, 
 wherein the partial pressure of the methane, ethane, propane, butane, pentane or hexane is 180 torr and the gas has a total pressure of 780 torr. 
 
     
     
       2. The method of  claim 1 , wherein the metal catalyst comprises a Group V metal, a Group VI metal, a Group VII metal, a Group VIII metal, a lanthanide, a transition metal, or a mixture thereof. 
     
     
       3. The method of  claim 2 , wherein the metal catalyst comprises Fe and a second metal, wherein the second metal is V, Nb, Cr, W, Mo, Mn, Re, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt, Ce, Eu, Er, Yb, Ag, Au, Zn, Cd, Sc, Y, La, or a mixture thereof. 
     
     
       4. The method of  claim 3 , wherein the second metal comprise Ni, Co, Cr, Mo, or a mixture thereof. 
     
     
       5. The method of  claim 4 , wherein the metal catalyst comprises a mixture of Fe and Mo. 
     
     
       6. The method of  claim 1 , wherein the support comprises a powdered oxide. 
     
     
       7. The method of  claim 6 , wherein the powdered oxide comprises Al 2 O 3 , SiO 2 , MgO, or zeolites. 
     
     
       8. The method of  claim 7 , wherein the powdered oxide comprises Al 2 O 3 . 
     
     
       9. The method of  claim 1 , wherein the metal catalyst and the support are in a mass ratio of about 1:10 to about 1:20. 
     
     
       10. The method of  claim 1 , wherein the gas comprises methane. 
     
     
       11. The method of  claim 1 , wherein the gas further comprises an inert gas. 
     
     
       12. The method of  claim 11 , wherein the inert gas comprises argon, helium, nitrogen, or a mixture thereof. 
     
     
       13. The method of  claim 1  wherein the reaction temperature is between about 800° C. and 900° C.